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Files systems

NERSC's global home and project file systems are available on Franklin. Additionally, Franklin has over 400 TB of locally attached high-performance /scratch disk space  For information on the NERSC file systems, see the link at right.

Scratch File Systems

Aggregate Peak Performance # IO Servers Interconnect File System Software Disk Array Vendor
$SCRATCH 209 TB 17 GB/sec
Lustre DDN
$SCRATCH2 209 TB 17 GB/sec 24
Lustre DDN


There are two Lustre file systems on the Franklin system mounted as /scratch and /scratch2.  They both have the same configuration.

  • 12 DDN S2A9550 disk controllers per file system
  • Each disk controller is served by 2 I/O servers called OSSs (Object Storage Servers)
  • Each OSS host 2 OSTs (Object Storage Target) which a user can think of as a software abstraction of a physical disk

In total each /scratch file system has 48 OSTs which is the lowest layer with which users need to interact.  When a file is created in /scratch it is "striped" or split across two different OSTs, which is the default.  Lustre file systems at other computing centers may set a different default based on their workload.  Striping is a technique to increase I/O performance.  Instead of writing to a single disk, striping to two disks allows the user to potentially double read and write bandwidth.